Metabolite-selective hyperpolarized 13C imaging using extended chemical shift displacement at 9.4 T

Abstract

Purpose To develop a technique for frequency-selective hyperpolarized 13C metabolic imaging in ultra-high field strength which exploits the broad spatial chemical shift displacement in providing spectral and spatial selectivity. Methods The spatial chemical shift displacement caused by the slice-selection gradient was utilized in acquiring metabolite-selective images. Interleaved images of different metabolites were acquired by reversing the polarity of the slice-selection gradient at every repetition time, while using a low-bandwidth radio-frequency excitation pulse to alternatingly shift the displaced excitation bands outside the imaging subject. Demonstration of this technique is presented using 1H phantom and in vivo mouse renal hyperpolarized 13C imaging experiments with conventional chemical shift imaging and fast low-angle shot sequences. Results From phantom and in vivo mouse studies, the spectral selectivity of the proposed method is readily demonstrated using results of chemical shift spectroscopic imaging, which displayed clearly delineated images of different metabolites. Imaging results using the proposed method without spectral encoding also showed effective separation while also providing high spatial resolution. Conclusion This method provides a way to acquire spectrally selective hyperpolarized 13C metabolic images in a simple implementation, and with potential ability to support combination with more elaborate readout methods for faster imaging.

Flow‐suppressed hyperpolarized 13C chemical shift imaging using velocity‐optimized bipolar gradient in mouse liver tumors at 9.4 T

“…To suppress the vascular signal and reduce contamination coming from the vessel in hyperpolarized 13 C CSI, a velocity‐optimized bipolar gradient was implemented and applied to mouse liver. At an ultrahigh field (9.4 T), 13 C is short, on the order of 20 ms . For this reason, insertion of a bipolar gradient can induce severe ‐related signal loss in stationary tissue.…”

The use of hyperpolarized carbon-13 magnetic resonance for molecular imaging

“…CSDA can also be used along the slice selection orientation by using a small bandwidth frequency selective RF pulse excitation such that the displaced excitation band of the non-desired metabolites shifts outside of the coil [152]. This approach has advantages over SPSP RF pulses due its simplicity, but provides limited slice selection accuracy and the geometry of the coil and the subject size limits the imaging parameters.…”

High resolution hyperpolarized 13C MRSI using SPICE at 9.4T

“…In addition, spectral-spatial (SPSP) RF pulses that allow metaboliteselective excitation have been combined with flyback echo-planar readout gradient (12), spiral readout gradient (13), and balanced steady-state free precession sequence (14) to facilitate the rapid acquisition of metabolic images at the expense of frequency encoding. For ultrahigh field (e.g., 9.4T) environments, high-resolution metabolic imaging technique using the broad chemical shift displacement have been proposed (15). Furthermore, Weiss et al (16) adopted an advanced reconstruction method by exploiting spatial and temporal correlations combined with SPSP RF pulses and echo-planar readout.…”